Trying to identify a plant shown in Gardeners' World - help!

If anyone saw it, I'd be glad of a steer - it was an item on a flower-cutting business. Towards the end they showed a shot (uncaptioned - bah!) of a lovely herbaceous plant, in a clump with tall spires and leaves that were green but gradually blushing purple, so they looked like flowers but were actually leaves, iyswim.